The long-term objective of this research is to learn more about reproductive mechanisms and their evolution in acarines (mites and ticks) and other ectoparasites and/or disease vectors. Special attention is directed to ectoparasites and disease vectors of public health importance which exhibit different parasitic habits and reproductive strategies. Major research efforts focus on the human-biting ixodid ticks Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis (all vectors of several pathogens to man and other animals; D. variabilis is the major vector of Rocky Mountain Spotted Fever), the argasid tick Ornithodoros parkeri, and the chicken mite, Dermanyssus gallinae. Specific objectives are to: (1) describe, map and study the activity cycles of the neurosecretory cells (NSC) at various nutritional and reproductive stages of the acarines and to experimentally alter the NSC cycles by organ transplants, injections of insect hormones, etc. in vivo and in vitro; (2) study effects of hormones on development and reproduction in vivo and in vitro; (3) investigate the processes and stimuli causing spermatogenesis, spermiogenesis, sperm transfer and relocation; (4) investigate factors responsible for egg maturation and oviposition; (5) determine whether D. gallinae reproduces by haplodiploidy or parahaploidy. Descriptive and experimental approaches will be employed using in vivo and in vitro systems. Techniques will involve organ cultures, autoradiography, radioimmunoassay (RIA), scanning electron microscopy (SEM), histochemically treated tissue sections, gamma radiation, organ transplantations and injections, and chromosomal analyses.